Pauli-like magnetic susceptibility in emeraldine base polyaniline

Magnetic susceptibility measurements on emeraldine base (EB) polyaniline are found to exhibit a Pauli-like behavior up to a temperature of 475 K. A simple albeit physically realistic model involving spin-pairs is shown to lead to such a dependence on temperature. The analysis of the data indicates that polarons in EB are created in pairs and that the intra-pair interactions encompass a broad distribution of antiferromagnetic exchange couplings. The results on EB are further shown to have essential implications for a correct interpretation of the magnetic susceptibility data in doped conducting polymers.